CN108965185B - Method and device for hybrid modulation and demodulation of multiple carriers - Google Patents
Method and device for hybrid modulation and demodulation of multiple carriers Download PDFInfo
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Abstract
The embodiment of the invention discloses a method and a device for mixed modulation and demodulation of multiple carriers, wherein the method comprises the following steps: acquiring a serial bit stream, and performing first preprocessing on the serial bit stream to obtain a plurality of groups of target bit streams; respectively inputting each target bit stream into a corresponding Orthogonal Frequency Division Multiplexing (OFDM) modulation unit to obtain a plurality of corresponding subcarriers; combining a plurality of sub-carriers to obtain a multi-carrier, and sending the multi-carrier to a receiving end; wherein, a plurality of OFDM modulation units are connected in parallel to form a hybrid modulator of OFDM and FDM. The embodiment of the invention can make up for the shortfall by taking the advantages of the modulation of multiple carriers by mixing OFDM and FDM, thereby not only obtaining higher frequency spectrum utilization rate, but also not generating higher PAPR value.
Description
Technical Field
The embodiment of the invention relates to the technical field of communication, in particular to a method and a device for hybrid modulation and demodulation of multiple carriers.
Background
Because the range of the expanded utilization of information bearing resources such as time domain, space domain, code domain, power domain and the like is very limited, the amount of information borne by the resources cannot be increased in a breakthrough manner within a long time in the technology. It is expected that during the 5G application period, the frequency domain will still be the main information bearing resource for bearing high speed, high bandwidth and high data volume in wireless communication, especially the millimeter wave that may be applied to 5G system, because it has the obvious advantage of several GHz with low cost, even completely free bandwidth, and can push the multi-carrier transmission technology to wider application environment. Therefore, researching the utilization rate of frequency domain resources, expanding the application range of new frequency domain resources, overcoming the related difficulties in frequency division multiplexing, will still be an important issue in multicarrier transmission technology.
The broadband communication is a multi-carrier transmission technology, and the system divides a broadband channel into a plurality of narrowband channels, divides a broadband carrier into a plurality of subcarriers, and utilizes each narrowband channel to carry or modulates each information to be transmitted by each subcarrier, so the broadband communication technology is also called as a frequency division multiplexing technology. The early frequency division multiplexing technology requires that a plurality of narrow-band subcarriers generated by a plurality of oscillators cannot interfere with each other, the interval between the subcarriers is large, the number of narrow-band subcarriers divided by a broadband carrier is small, and the frequency spectrum utilization rate is not high. If all narrow-band subcarriers in broadband communication can be orthogonal to each other, and all subcarriers have no interference, not only can the guard interval between the subcarriers be cancelled, but also the subcarriers can be overlapped with each other, and the frequency spectrum utilization rate of the broadband carriers can be greatly improved.
An IFFT/FFT-based OFDM (Orthogonal Frequency Division Multiplexing) technology is currently the Frequency Division Multiplexing technology with the highest Frequency domain utilization rate, and will also be one of the important application technologies in 5G and subsequent periods. The IFFT/FFT algorithm makes it possible to divide the wideband carrier into subcarriers, and the bandwidths of the divided subcarriers are completely the same, and the simultaneity when the subcarriers are transmitted is also very high, more importantly, the algorithm is simple and fast. However, the subcarriers divided by the IFFT/FFT algorithm may cause a severe PAPR (Peak to Average Power Ratio) when combined. FDM (Frequency Division Multiplexing) is also a multi-carrier transmission technology that is mature in technology and widely used, and has no PAPR although the spectrum utilization rate is low.
In the process of implementing the embodiment of the present invention, the inventor finds that the subcarriers divided by the existing OFDM algorithm may bring a severe PAPR when combined, and the existing FDM spectrum is low in utilization rate.
Disclosure of Invention
Because the prior art has the above problems, embodiments of the present invention provide a method and an apparatus for hybrid modulating and demodulating multiple carriers.
In a first aspect, an embodiment of the present invention provides a method for hybrid modulating multiple carriers, including:
acquiring a serial bit stream, and performing first preprocessing on the serial bit stream to obtain a plurality of groups of target bit streams;
respectively inputting each target bit stream into a corresponding Orthogonal Frequency Division Multiplexing (OFDM) modulation unit to obtain a plurality of corresponding subcarriers;
combining a plurality of sub-carriers to obtain a multi-carrier, and sending the multi-carrier to a receiving end;
wherein, a plurality of OFDM modulation units are connected in parallel to form a hybrid modulator of OFDM and FDM.
Optionally, the respectively inputting each target bit stream into the corresponding OFDM modulation unit to obtain a plurality of corresponding subcarriers specifically includes:
and respectively inputting each target bit stream into a corresponding OFDM modulation unit, and sequentially carrying out constellation mapping, pilot frequency insertion, serial-parallel conversion, subcarrier mapping, N-point inverse discrete Fourier transform, parallel-serial conversion, cyclic prefix insertion, low-pass filtering, digital-to-analog conversion and up-conversion processing to obtain a plurality of corresponding subcarriers.
Optionally, the combining the multiple subcarriers to obtain a multicarrier, and sending the multicarrier to a receiving end, specifically including:
combining a plurality of sub-carriers to obtain a multi-carrier, performing radio frequency amplification processing on the multi-carrier, and sending the multi-carrier after the radio frequency amplification processing to a receiving end.
In a second aspect, an embodiment of the present invention provides a method for hybrid demodulation of multiple carriers, including:
receiving multiple carriers, and grouping the multiple carriers to obtain a plurality of sub-carriers;
respectively inputting a plurality of subcarriers into corresponding OFDM demodulation units to obtain a plurality of corresponding target bit streams;
performing second preprocessing on the plurality of target bit streams to obtain serial bit streams;
wherein, a plurality of OFDM demodulation units are connected in parallel to form a hybrid demodulator of OFDM and FDM.
Optionally, the respectively inputting the multiple subcarriers into corresponding OFDM demodulation units to obtain multiple corresponding target bit streams includes:
and respectively inputting a plurality of sub-carriers into corresponding OFDM demodulation units, and sequentially carrying out up-conversion, analog-to-digital conversion, low-pass filtering, cyclic prefix removal, serial-to-parallel conversion, N-point inverse discrete Fourier transform, sub-carrier inverse mapping, parallel-to-serial conversion, channel compensation and constellation inverse mapping to obtain a plurality of corresponding target bit streams.
In a third aspect, an embodiment of the present invention further provides an apparatus for hybrid modulating multiple carriers, including:
the first bit stream processing module is used for acquiring a serial bit stream and performing first preprocessing on the serial bit stream to obtain a plurality of groups of target bit streams;
the subcarrier modulation module is used for respectively inputting each target bit stream into the corresponding orthogonal frequency division multiplexing OFDM modulation unit to obtain a plurality of corresponding subcarriers;
the multi-carrier acquisition module is used for combining a plurality of sub-carriers to obtain a multi-carrier and sending the multi-carrier to a receiving end;
wherein, a plurality of OFDM modulation units are connected in parallel to form a hybrid modulator of OFDM and FDM.
Optionally, the subcarrier modulation module is specifically configured to input each target bit stream into a corresponding OFDM modulation unit, and perform constellation mapping, pilot frequency insertion, serial-to-parallel conversion, subcarrier mapping, N-point inverse discrete fourier transform, parallel-to-serial conversion, cyclic prefix insertion, low-pass filtering, digital-to-analog conversion, and up-conversion in sequence to obtain a plurality of corresponding subcarriers.
Optionally, the multi-carrier obtaining module is specifically configured to combine a plurality of sub-carriers to obtain a multi-carrier, perform radio frequency amplification on the multi-carrier, and send the multi-carrier after the radio frequency amplification to a receiving end.
In a fourth aspect, an embodiment of the present invention further provides an apparatus for hybrid demodulation of multiple carriers, including:
the multi-carrier processing module is used for receiving multi-carriers, and grouping the multi-carriers to obtain a plurality of sub-carriers;
the subcarrier demodulation module is used for respectively inputting a plurality of subcarriers into corresponding OFDM demodulation units to obtain a plurality of corresponding target bit streams;
the second bit stream processing module is used for carrying out second preprocessing on a plurality of target bit streams to obtain serial bit streams;
wherein, a plurality of OFDM demodulation units are connected in parallel to form a hybrid demodulator of OFDM and FDM.
Optionally, the subcarrier demodulation module is specifically configured to input a plurality of subcarriers into corresponding OFDM demodulation units respectively, and perform up-conversion, analog-to-digital conversion, low-pass filtering, cyclic prefix removal, serial-to-parallel conversion, N-point inverse discrete fourier transform, subcarrier inverse mapping, parallel-to-serial conversion, channel compensation, and constellation inverse mapping in sequence to obtain a plurality of corresponding target bit streams.
In a fifth aspect, an embodiment of the present invention further provides an electronic device, including:
at least one first processor; and
at least one first memory communicatively coupled to the first processor, wherein:
the first memory stores first program instructions executable by the first processor, the first processor invoking the first program instructions to perform the method of any of the corresponding claims.
In a sixth aspect, embodiments of the present invention also provide a non-transitory computer readable storage medium storing a first computer program, the first computer program causing the first computer to perform the method of any one of the corresponding claims.
In a seventh aspect, an embodiment of the present invention further provides an electronic device, including:
at least one second processor; and
at least one second memory communicatively coupled to the second processor, wherein:
the second memory stores second program instructions executable by the second processor, the second processor invoking the second program instructions to perform the method of any of the corresponding claims.
In an eighth aspect, embodiments of the present invention also provide a non-transitory computer-readable storage medium storing a second computer program, the second computer program causing the computer to perform the method of any one of the corresponding claims.
According to the technical scheme, the embodiment of the invention can make up for the shortfall by mixing the OFDM and the FDM for multi-carrier modulation, thereby not only obtaining higher spectrum utilization rate, but also not generating higher PAPR value.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a flowchart illustrating a method for hybrid modulating multiple carriers according to an embodiment of the present invention;
fig. 2 is a flowchart illustrating a method for hybrid demodulation of multiple carriers according to an embodiment of the present invention;
fig. 3 is a flowchart illustrating a method for hybrid modulating and demodulating multiple carriers according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a spectrum design of a method for hybrid modulating multiple carriers according to an embodiment of the present invention;
fig. 5 is a schematic diagram of transmission waveforms of the 1 st OFDM modulation and demodulation unit in the method for hybrid modulating multiple carriers according to an embodiment of the present invention;
fig. 6 is a schematic diagram of transmission waveforms of the 2 nd OFDM modulation and demodulation unit in the method for hybrid modulating multiple carriers according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a transmission waveform of a 3 rd OFDM modulation and demodulation unit in a method for hybrid modulating multiple carriers according to an embodiment of the present invention;
FIGS. 8(A) and (B) are schematic diagrams illustrating bit error rates of an up-converted analog signal and a received binary code sink, respectively, in a method for hybrid modulating multiple carriers according to an embodiment of the present invention;
fig. 9(a) and (B) are schematic diagrams illustrating bit error rates of 7 subcarriers and 10 subcarriers, respectively, in a method for hybrid modulating multiple carriers according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of an apparatus for hybrid modulating multiple carriers according to an embodiment of the present invention;
fig. 11 is a schematic structural diagram of an apparatus for hybrid demodulation of multiple carriers according to an embodiment of the present invention.
FIG. 12 is a logic block diagram of an electronic device according to an embodiment of the invention;
fig. 13 is a logic block diagram of an electronic device according to another embodiment of the present invention.
Detailed Description
The following further describes embodiments of the present invention with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Fig. 1 shows a flowchart of a method for hybrid modulating multiple carriers provided in this embodiment, including:
s101, obtaining a serial bit stream, and performing first preprocessing on the serial bit stream to obtain a plurality of groups of target bit streams.
Wherein the serial bit stream is an original bit stream input by a transmitting terminal.
The first pre-processing comprises: channel coding processing, interleaving processing and grouping processing.
The target bit stream is a bit stream obtained by performing first preprocessing on a serial bit stream; the target bit stream comprises a plurality of groups, and each group of target bit streams is input into one OFDM modulator.
And S102, respectively inputting each target bit stream into a corresponding Orthogonal Frequency Division Multiplexing (OFDM) modulation unit to obtain a plurality of corresponding subcarriers.
The OFDM modulation units are connected in parallel to form a hybrid modulator of OFDM and FDM, and each OFDM modulation unit is independent to modulate each target bit stream to obtain a subcarrier corresponding to each target bit stream.
S103, combining the plurality of sub-carriers to obtain a multi-carrier, and sending the multi-carrier to a receiving end.
The multi-carrier is obtained by combining sub-carriers obtained by modulating by the OFDM modulation unit.
The receiving end is a terminal for receiving the multi-carrier.
In this embodiment, the OFDM and FDM are mixed to perform multi-carrier modulation, so that the advantages and the disadvantages can be made up, and a higher spectrum utilization rate can be obtained without generating a higher PAPR value.
Further, on the basis of the above method embodiment, S102 specifically includes:
and respectively inputting each target bit stream into a corresponding OFDM modulation unit, and sequentially carrying out constellation mapping, pilot frequency insertion, serial-parallel conversion, subcarrier mapping, N-point inverse discrete Fourier transform, parallel-serial conversion, cyclic prefix insertion, low-pass filtering, digital-to-analog conversion and up-conversion processing to obtain a plurality of corresponding subcarriers.
And carrying out various OFDM related processing on each target bit stream through each independent OFDM modulation unit to obtain corresponding subcarriers.
Further, on the basis of the above method embodiment, S103 specifically includes:
combining a plurality of sub-carriers to obtain a multi-carrier, performing radio frequency amplification processing on the multi-carrier, and sending the multi-carrier after the radio frequency amplification processing to a receiving end.
The radio frequency amplification processing is to amplify the radio frequency signal of the multi-carrier so as to reduce the loss in the multi-carrier transmission process.
Fig. 2 shows a flowchart of a method for hybrid demodulation of multiple carriers according to this embodiment, which includes:
s201, receiving multiple carriers, and obtaining a plurality of sub-carriers after grouping the multiple carriers.
Wherein, the multi-carrier is transmitted by a transmitting terminal.
The step is the reverse process of step S103, i.e. grouping the multiple carriers obtained after combining the subcarriers, and obtaining each subcarrier again.
S202, inputting the plurality of sub-carriers into corresponding OFDM demodulation units respectively to obtain a plurality of corresponding target bit streams.
The step is the reverse process of step S102, that is, the modulated subcarriers are demodulated to obtain each target bit stream again.
S203, after second preprocessing is carried out on the plurality of target bit streams, serial bit streams are obtained.
The step is the reverse process of step S101, that is, the target bit stream is subjected to the second preprocessing to obtain the serial bit stream.
Wherein, a plurality of OFDM demodulation units are connected in parallel to form a hybrid demodulator of OFDM and FDM.
The second pre-processing comprises: combining processing, de-interleaving processing and channel coding processing.
In this embodiment, the OFDM and FDM are mixed to perform multi-carrier modulation, so that the advantages and the disadvantages can be made up, and a higher spectrum utilization rate can be obtained without generating a higher PAPR value.
Further, on the basis of the above method embodiment, S202 specifically includes:
and respectively inputting a plurality of sub-carriers into corresponding OFDM demodulation units, and sequentially carrying out up-conversion, analog-to-digital conversion, low-pass filtering, cyclic prefix removal, serial-to-parallel conversion, N-point inverse discrete Fourier transform, sub-carrier inverse mapping, parallel-to-serial conversion, channel compensation and constellation inverse mapping to obtain a plurality of corresponding target bit streams.
And carrying out various OFDM demodulation related processing on each subcarrier through each independent OFDM demodulation unit to obtain a corresponding target bit stream.
Specifically, the "hybrid modulator of OFDM and FDM" and the "hybrid demodulator of OFDM and FDM" may be collectively referred to as "hybrid modem of OFDM and FDM".
OFDM and FDM belong to the same frequency division multiplexing technology. The OFDM has the advantage of high utilization rate of frequency spectrum resources, but has the defect of high PAPR value; FDM has no PAPR problem, but the spectrum resource utilization is low. The OFDM and the FDM are mixed for use, so that the advantages can be made up for the disadvantages, a high spectrum utilization rate can be obtained, a high PAPR value cannot be generated, and the aim can be achieved by a centralized OFDM and FDM mixed modulation multi-carrier technology. Because based on mature technologies such as OFDM and FDM, the technology difficulty and the development cost of the centralized OFDM and FDM mixed modulation multi-carrier are lower, the method is a novel technology in the field of multi-carrier transmission, and has high practical value. In the centralized OFDM and FDM mixed modulation multi-carrier technology, FDM modulation frequencies are distributed in a centralized mode, the blank space between the modulation frequencies is only FDM protection intervals, and blank useless frequency spectrums of the FDM protection intervals can be properly adjusted according to the requirements of practical application scenes, so that the mutual influence of the FDM modulation frequencies among OFDM modules is not large, the occupation of the blank useless frequency spectrums can be reduced to the greatest extent, particularly the continuity of frequency spectrum resource application, and the management and maintenance of system frequency spectrums can be facilitated.
The principle of OFDM and FDM hybrid modulation multi-carrier is described below:
the PAPR of the digital OFDM modulated signal based on IFFT/FFT is too high, mainly related to the synchronization of the digitally modulated subcarriers and the linear correlation of the carrying signal, especially the larger number of subcarriers, because the larger the number of subcarriers, the higher the PAPR.
The synchronization, the homogeneity and the linear correlation among the subcarriers in the analog FDM modulation process are small, the subcarriers are not overlapped, the guard interval is provided, the number of the subcarriers is small, and the problem of PAPR is solved.
OFDM and FDM belong to the frequency division multiplexing technology, the technology is mature, and the realization difficulty is low. If the two are mixed for use, the advantages can be obtained and the disadvantages can be compensated, and a new technical choice is provided for reducing the high PAPR value in OFDM based on IFFT/FFT mode.
Fig. 3 shows the technical principle of the IFFT/FFT-based OFDM and FDM hybrid modulation multi-carrier, wherein the IFFT/FFT-based OFDM modulation modules are dedicated OFDM modules, each module can frequency-division multiplex N orthogonal subcarriers, the bandwidth of each subcarrier is the same, the frequency-division multiplexed digital orthogonal subcarriers of each module are the same, and all modules are the same. If each OFDM modulation module is regarded as a link for processing one path of signals and the links have enough bandwidth intervals to ensure that the paths of signals are not influenced mutually, the M paths of signal processing links are combined, the structure is an FDM modulator, and the number of subcarriers supported by the OFDM and FDM mixed modulation multicarrier transmitter is N multiplied by M.
At the transmitting end, after the serial bit stream is processed by channel coding and interleaving, the serial bit stream is divided into M groups of bit streams with the same length by the system, and each group of bit streams can form N groups of bit streams after constellation mapping1A mapping symbol is inserted into N2After pilot, make N1+N2N, exactly the number of subcarriers. It can be seen that, in the kth OFDM modulation unit, the system forms mapping symbols through constellation mapping, inserts pilot frequency, and then forms N parallel sub-mapping symbols through serial-to-parallel conversion, and then performs subcarrier mapping to make N sub-symbols and N-point IFFT function to generate 1 OFDM symbol modulated by N orthogonal subcarriers, inserts CP, and completes the modulation of the kth OFDM modulation unit through low pass filter and digital-to-analog conversion. Followed by FDM analog modulation, the system using the starting frequency f of the k-th carrier bandminkModulating the kth OFDM symbol carried by N subcarriers in parallel, finally combining the M OFDM symbols into M OFDM symbols transmitted by NxM subcarriers in parallel by the system, sending the M OFDM symbols into an input frequency amplifier, and sending the M OFDM symbols into a transmitting antenna for radio frequency output.
Obviously, at the transmitting end, each OFDM modulation unit modulates 1 mapping symbol into 1 OFDM symbol of the time domain in the frequency domain, and transmits 1 OFDM symbol in parallel using N subcarriers at the same time; the FDM modulator uses M up-conversion to modulate M analog signals containing 1 OFDM symbol, uses M up-conversion to transmit M OFDM symbol analog signals at the same time, realizes multi-carrier transmission of M OFDM symbol analog signals at the same time in time domain by NxM sub-carriers, and limits PAPR value in the range of 1 OFDM module.
At the receiving end, after the analog signal is affected by wireless channel and noise, the antenna receives only weak signal, the system is firstly amplified by low noise amplifier with very low noise coefficient, then the amplified signal is sent to the frequency fmin1、fmin2、…、fmink、…、fminMFrequency conversion of the down-converter in order to restore the frequency of the N parallel sub-carriers carrying 1 OFDM symbol into f1＝Δf、f2＝2Δf、…、fk＝kΔf、…、fNEach OFDM demodulation unit divides 1 OFDM symbol into N sub-OFDM symbols through analog-to-digital conversion, low-pass filtering, CP removal and time domain serial-to-parallel conversion, the N sub-OFDM symbols are demodulated into N inverse mapping symbols consisting of N1+ N2 through N-point FFT, the demodulation work of the OFDM demodulation unit is completed through parallel-to-serial conversion, correct channels are recovered through channel compensation, and N is removed2After pilot frequency, recovering the mapping symbol into group bit stream through constellation inverse mapping, finally combining the M group bit streams according to the sequence of the transmitting end by a group combining system, and recovering serial bit stream output after de-interleaving and channel decoding.
Obviously, at the receiving end, the FDM demodulator first demodulates M analog signals containing M OFDM symbols using M down-conversion, so that each OFDM demodulation module obtains its corresponding analog signal containing 1 OFDM symbol, and recovers 1 OFDM symbol through analog-to-digital conversion; each OFDM demodulation module demodulates 1 OFDM symbol into 1 mapping symbol in the frequency domain in the time domain, restores N sub-OFDM symbols transmitted simultaneously using N subcarriers to N mapping symbols in the corresponding frequency domain, and finally restores the original serial bit stream from the N × M mapping symbols.
According to the illustration in fig. 4, the frequency spectrum of the technique for localized OFDM and FDM hybrid modulation of multiple carriers can be denoted as fmin1＝Fmin、fmin2＝Fmin+ΔF、…、fmink＝Fmin+(k-1)ΔF、…、fminM＝Fmin+ (M-1) Δ F, wherein FminIs the minimum available frequency point of the carrier, and is the bandwidth of the OFDM module (including the sub-carrier occupied bandwidth and FDM protection in the OFDM module)Guard bandwidth). If the standard threshold value of 6dB is adopted by the system, the optimal sampling number N of IFFT/FFT in the OFDM module is 256 to make the PAPR value of each OFDM module meet the requirement of the expected value. If the GSM and LTE frequency point selection specifications are used as reference, the sub-carrier bandwidth Δ F in the OFDM module is 15KHz, and the FDM protection bandwidth is 7 × Δ F105 KHz, so that the bandwidth Δ F of the optimum standard OFDM module is N × Δ F +105KHz 3.945 MHz. It can be seen that the minimum frequency point FminAnd the number of OFDM modules M is determined according to the bandwidth of the selected carrier frequency.
According to the potentially available frequency band planning of IMT, the range of the 6GHz band that may become the 5G system spectrum is 5925 + 7145MHz, and the bandwidth is 1.22GHz, if the spectrum is divided by taking the best standard OFDM module as a unit, the number M of the OFDM modules that the spectrum can support is 309, and the remaining 995KHz can be used as the sidebands of the total spectrum, that is, 497.5KHz sideband bandwidth is reserved on each side of the total spectrum. Minimum available frequency point FminThe up-conversion modulation frequency of the M OFDM modules is f respectively at 5925.4975MHzmin1＝Fmin＝5925.4975MHz、fmin2＝Fmin+ΔF＝5929.4425MHz、…、fminM＝FminAnd + (M-1) Δ F-7140.5575 MHz. Because the actual number of subcarriers is 180 when the best sampling value N is 256, the technology of centralized OFDM and FDM mixed modulation multicarrier is used to process the 6GHz band, the total number of actually supportable subcarriers is up to 55620, and 309 OFDM symbols can be simultaneously transmitted in parallel in 1 OFDM symbol period.
As can be seen from fig. 4, localized refers to the upconversion f in FDM modulationmin1、fmin2、…、fminMThe equal frequency points are continuously and intensively distributed, the frequency spectrum range of the whole carrier is divided into subcarriers except for the sidebands and the protective bandwidth, and therefore the frequency spectrum utilization rate of the centralized OFDM and FDM mixed modulation multicarrier technology is high. Of course, a whole block of spectrum resources may also be divided into only a part of frequency bands for use in multicarrier transmission according to actual scene needs, and another part may be left for other use or reservation.
From the aspect of spectrum division, the centralized type is suitable for the split type application of the spectrum, and the waste of the spectrum resources generated by the centralized type is minimum; from the aspect of operation efficiency, the method is suitable for application scenarios in which the total bandwidth redundancy of the carrier is not very large, but the system response speed is required to be faster and the reliability is required to be higher.
The centralized OFDM and FDM mixed modulation multi-carrier technology has the advantages of high frequency spectrum utilization rate, simple frequency point sequencing, small technical difficulty, good performance and higher system operation rate. If the frequency spectrum resources are slightly loose, the FDM protection bandwidth can be properly increased, the indirect mutual interference of OFDM modules is reduced, the error rate in the multi-carrier transmission process is reduced, and the performance of the system is improved.
According to the calculation resource and the above design standard, taking the OFDM module M as 3, the subcarrier N as 64, the subcarrier bandwidth Δ F as 15KHz, the FDM guard interval as 105KHz, the OFDM module bandwidth Δ F as 1.065MHz, the constellation mapping as 16QAM, the wireless channel signal-to-noise ratio SNR as 10dB, and the minimum frequency point of the up-down frequency conversion as Fmin5925.4975MHz, 3 up-and-down frequency conversions are respectively fmin1＝Fmin＝5925.4975MHz、fmin2＝Fmin+ Δ F and Fmin3＝Fmin+2 Δ F. Taking a subframe 1000, 14 OFDM symbols per subframe, 4 bits of information per OFDM symbol, the binary code transmitted by the source is 3 × 64 × 1000 × 14 × 4-10.752 Mbit, each group of binary codes after 3 groups is 3.584Mbit, and the OFDM symbol processed by each OFDM module is 896K.
The whole simulation process is divided into a transmitting end and a receiving end. A transmitting end: the system generates 10.752Mbit binary data information source, equally divides the information source into 3.584Mbit binary numbers of each group according to the number M of OFDM modules, converts each group of binary codes into 1.792M mapping symbols of non-return-to-zero codes, maps 1.792M mapping symbols into 896K complex mapping symbols through 16QAM constellation mapping, performs IFFT on 896K complex mapping symbols by using 64 subcarrier repetition to convert into 896K complex OFDM symbols, modulates the 896K complex OFDM symbols into analog signals by using up-conversion, superposes three groups of analog signals and then transmits the signals, and adds white noise in a wireless channel; receiving end: and demodulating 3 groups of superposed noisy signals by using 3 down-conversion respectively, recovering each and corresponding analog signal, recovering the analog signal into an OFDM symbol after mean value sampling, recovering the OFDM symbol into a mapping symbol through FFT (fast Fourier transform), recovering the mapping symbol into a non-return-to-zero code through constellation inverse mapping, recovering the mapping symbol into a binary data code through level conversion, and finally recombining the binary codes recovered by each group of OFDM modules into data information in sequence to output.
Taking the 1 st OFDM modulation and demodulation unit in fig. 5 as an example, it can be seen that the transmission codes shown in fig. 5.1 and fig. 5.2 are completely different from non-return-to-zero codes, the former is a binary code in units of bits, the latter is a 4-level code in units of dibits, but both are one-dimensional data streams. Fig. 5.3 shows a mapping symbol corresponding to a complex level code after constellation mapping, fig. 5.4 shows a complex OFDM symbol after IFFT transformation, both are planar complex codes, and it should be noted that two-dimensional complex information must be superimposed into one-dimensional data in the time domain and modulated into an analog signal by up-conversion, and then the analog signal can be transmitted through a power amplifier, that is, the two-dimensional complex OFDM symbol must be converted into a one-dimensional OFDM symbol before up-conversion modulation. Fig. 5.5 is a one-dimensional signal after discrete sampling of the upconverted analog signal.
Fig. 5.6 shows that white noise is added to the up-conversion analog signal, and it should be noted that the white noise signal is a signal obtained by adding white noise to the up-conversion analog signal after adding white noise to the up-conversion analog signal of 3 OFDM modules, and the white noise signals of the 3 OFDM modules are completely the same because the values of the white noise signals are in the same interval. The 3 identical whitened signals are respectively sent to 3 OFDM modules, and are demodulated by 3 different down-conversion frequencies to generate 3 different down-converted signals (fig. 5.7). Fig. 5.8 shows a two-dimensional complex OFDM symbol after FFT transformation of the down-converted signal, which diverges due to white noise, and the received signal has changed from the point signal of the transmitted signal to the surface signal. Fig. 5.9 shows the constellation inverse mapping, and the signal is restored to a level complex signal. Fig. 5.10 shows the recovered received signal, which is identical to the original transmitted signal.
The operation of the OFDM modulation and demodulation units (module 1, module 2 and module 3 in fig. 8, respectively) of fig. 5, 6 and 7, respectively, for 3 packets, is according to the transmission waveforms at the reference numerals of fig. 3. It can be seen that the transmission signals of 3 groups are completely different, the non-return-to-zero code after transformation, the OFDM symbol after IFFT transformation, and the analog signal after up-conversion modulation are also completely different in the diagram, but the transmission signal affected by white noise or white noise after combination is the same, the mapping symbols after down-conversion demodulation and FFT transformation are different, but the constellation mapping signal and the constellation inverse mapping signal in the 3 OFDM modulation and demodulation units are completely the same because the level transformation and the inverse transformation are completely equivalent. Each OFDM modulation and demodulation unit transmits the same signal as the received signal, but the 3 OFDM modulation and demodulation units are completely different.
Fig. 8(a) and (B) are waveform diagrams showing several key points in the transmission and reception process of the centralized OFDM and FDM mixed multi-carrier transmission technology, and only 30 bits and 30 symbol references are taken here. It can be seen that a 30-bit transmission binary code is completely the same as a reception binary code, and the middle of the 30-bit transmission binary code is respectively subjected to multicarrier transmission with 64 mutually orthogonal subcarriers by 3 OFDM modules, and transmission information of the 3 OFDM modules is combined during up-conversion, as shown in fig. 8(a), because of analog modulation, a signal corresponding to 30 OFDM symbols is also an analog signal, a noise-added signal subjected to noise influence is also an analog signal, the noise-added signal is re-divided into down-converted analog signals corresponding to 3 OFDM modules after down-conversion, a digital mapping symbol is restored after mean value and FFT conversion, a binary code corresponding to a constellation is restored after constellation de-mapping, and finally, the binary codes of the 3 OFDM modules are combined into a reception binary code of a signal sink, as shown in fig. 8 (B).
Fig. 5 to 8 simulate that although the basic principle of the centralized OFDM and FDM mixed multi-carrier transmission technology in the transmission and reception process can be reflected, and the situation of the technology in the transmission process can be helped to be known from the aspect of waveform change, the transmission performance of the technology in the whole simulation cannot be fully reflected because only a part of signals are actually presented. FIG. 9 is a bit error rate curve of the localized OFDM and FDM hybrid multi-carrier transmission under the above simulation conditions, where the modulated carrier f is shown in FIG. 9(A)min1、fmin2、fmin3Guard bandwidth in between is 7 sub-carriers, modulated carrier f shown in fig. 9(B)min1、fmin2、fmin3The guard bandwidth is 10 sub-carriers, and it can be seen that the bit error rate of the right graph is obviousCompared with the left figure, the bit error rate is reduced by 2 orders of magnitude by only increasing the width of 3 subcarriers, which shows that the influence of the size of the guard bandwidth on the modulation signals of the OFDM module is very large.
Compared with the F-OFDM technology of the 5G candidate technology, the OFDM and FDM mixed multi-carrier transmission technology adopts the up-conversion FDM technology, all OFDM modules are the same, the multi-analog modulation carrier is only applied during up-conversion, the multi-analog demodulation carrier is only applied during down-conversion, and a complex filtering group is not needed, so that the system structure is facilitated, the technical difficulty is simplified, and the OFDM and FDM mixed multi-carrier transmission technology can be used as one of the 5G candidate core technologies.
The centralized OFDM and FDM mixed multi-carrier transmission technology concentrates the basic advantages of OFDM and FDM, and on one hand, the high-frequency spectrum utilization rate of orthogonal subcarriers in OFDM is utilized, on the other hand, the subcarriers in FDM are not overlapped with each other and are provided with a guard interval to avoid overhigh PAPR. The centralized OFDM and FDM mixed multi-carrier transmission technology is a comprehensive frequency division multiplexing transmission mode mixed with FDM based on OFDM modules, sub-carriers in each OFDM module are orthogonal to each other, the frequency spectrum utilization rate of each OFDM module is greatly improved, and a protection interval is reserved among all used OFDM modules, so that the influence among the OFDM modules is reduced or even eliminated, and the influence of PAPR is limited in the OFDM modules.
The centralized OFDM and FDM hybrid multi-carrier transmission technique actually trades off a small amount of spectrum utilization for lower PAPR. Or a small amount of guard intervals in the frequency domain are used for replacing the PAPR to be only limited in the OFDM module, the PAPR of the OFDM module is limited by adjusting the number of subcarriers in the OFDM module or other suppression technologies, and then the plurality of OFDM modules are applied in parallel by the FDM technology based on different up-conversion, so that the system can realize the multi-carrier transmission with a lower PAPR value, and even the PAPR value is unrelated to the number of the OFDM modules. In addition, the centralized OFDM and FDM hybrid multi-carrier transmission technology is based on the OFDM technology and the FDM technology, so that the technology is a novel technology which is mature and low in implementation difficulty.
The up-conversion frequency points in the technology of the centralized OFDM and FDM mixed modulation multi-carrier are distributed in a centralized mode, the frequency points are simple to sequence, the technical difficulty is low, the running speed of the system is high, the frequency spectrum utilization rate is high, the frequency spectrum resource waste is little, and the method is very suitable for application scenarios where the total bandwidth redundancy of the carrier is not very high, but the system response speed requirement is higher, and the reliability requirement is higher. If the frequency spectrum resources are slightly loose, the FDM protection bandwidth can be properly increased, the indirect mutual interference of OFDM modules is reduced, the error rate in the multi-carrier transmission process is reduced, and the performance of the system is improved. In a word, the greatest advantages of the centralized OFDM and FDM hybrid modulation multi-carrier technology are high spectrum utilization rate, simple system processing, and therefore good performance, but low flexibility, and the centralized spectrum distribution directly affects the upgrading and capacity expansion of the system according to the application scenario service development needs.
Fig. 10 shows a schematic structural diagram of an apparatus for hybrid modulating multiple carriers according to this embodiment, where the apparatus includes: a first bitstream processing module 1001, a subcarrier modulation module 1002, and a multicarrier acquisition module 1003, wherein:
the first bit stream processing module 1001 is configured to obtain a serial bit stream, and perform first preprocessing on the serial bit stream to obtain a plurality of groups of target bit streams;
the subcarrier modulation module 1002 is configured to input each target bit stream into a corresponding OFDM modulation unit, respectively, to obtain a plurality of corresponding subcarriers;
the multi-carrier obtaining module 1003 is configured to combine a plurality of sub-carriers to obtain a multi-carrier, and send the multi-carrier to a receiving end;
wherein, a plurality of OFDM modulation units are connected in parallel to form a hybrid modulator of OFDM and FDM.
Specifically, the first bitstream processing module 1001 obtains a serial bitstream, and performs a first preprocessing on the serial bitstream to obtain a plurality of groups of target bitstreams; the subcarrier modulation module 1002 inputs each target bit stream into a corresponding orthogonal frequency division multiplexing OFDM modulation unit, respectively, to obtain a plurality of corresponding subcarriers; the multi-carrier obtaining module 1003 combines a plurality of sub-carriers to obtain a multi-carrier, and sends the multi-carrier to a receiving end.
In this embodiment, the OFDM and FDM are mixed to perform multi-carrier modulation, so that the advantages and the disadvantages can be made up, and a higher spectrum utilization rate can be obtained without generating a higher PAPR value.
Further, on the basis of the above device embodiment, the subcarrier modulation module 1002 is specifically configured to input each target bit stream into a corresponding OFDM modulation unit, and perform constellation mapping, pilot frequency insertion, serial-to-parallel conversion, subcarrier mapping, N-point inverse discrete fourier transform, parallel-to-serial conversion, cyclic prefix insertion, low-pass filtering, digital-to-analog conversion, and up-conversion in sequence to obtain a plurality of corresponding subcarriers.
Further, on the basis of the above device embodiment, the multi-carrier obtaining module 1003 is specifically configured to combine a plurality of sub-carriers to obtain a multi-carrier, perform radio frequency amplification processing on the multi-carrier, and send the multi-carrier after the radio frequency amplification processing to the receiving end.
The apparatus for hybrid modulation of multiple carriers described in this embodiment may be configured to perform the corresponding method embodiments, and the principle and technical effect are similar, which are not described herein again.
Fig. 11 shows a schematic structural diagram of an apparatus for hybrid demodulation of multiple carriers according to this embodiment, where the apparatus includes: a multicarrier processing module 1101, a subcarrier demodulation module 1102 and a second bitstream processing module 1103, wherein:
the multi-carrier processing module 1101 is configured to receive multiple carriers, and perform grouping processing on the multiple carriers to obtain a plurality of sub-carriers;
the subcarrier demodulation module 1102 is configured to input a plurality of subcarriers to corresponding OFDM demodulation units, respectively, to obtain a plurality of corresponding target bit streams;
the second bitstream processing module 1103 is configured to perform second preprocessing on a plurality of target bitstreams to obtain serial bitstreams;
wherein, a plurality of OFDM demodulation units are connected in parallel to form a hybrid demodulator of OFDM and FDM.
Specifically, the multi-carrier processing module 1101 receives multiple carriers, and performs packet processing on the multiple carriers to obtain a plurality of sub-carriers; the subcarrier demodulation module 1102 inputs a plurality of subcarriers into corresponding OFDM demodulation units, respectively, to obtain a plurality of corresponding target bit streams; the second bitstream processing module 1103 performs second preprocessing on a plurality of target bitstreams to obtain serial bitstreams.
In this embodiment, the OFDM and FDM are mixed to perform multi-carrier modulation, so that the advantages and the disadvantages can be made up, and a higher spectrum utilization rate can be obtained without generating a higher PAPR value.
Further, on the basis of the above device embodiment, the subcarrier demodulation module 1102 is specifically configured to input a plurality of subcarriers into corresponding OFDM demodulation units respectively, and perform up-conversion, analog-to-digital conversion, low-pass filtering, cyclic prefix removal, serial-to-parallel conversion, N-point inverse discrete fourier transform, subcarrier inverse mapping, parallel-to-serial conversion, channel compensation, and constellation inverse mapping in sequence to obtain a plurality of corresponding target bit streams.
The apparatus for hybrid demodulation of multiple carriers described in this embodiment may be used to implement the corresponding method embodiments described above, and the principle and technical effect are similar, which are not described herein again.
Referring to fig. 12, the electronic device includes: a first processor (processor)1201, a first memory (memory)1202, and a first bus 1203;
wherein,
the first processor 1201 and the first memory 1202 communicate with each other via the first bus 1203;
the first processor 1201 is configured to call a first program instruction in the first memory 1202 to execute the method provided by the corresponding method embodiments.
The present embodiments provide a non-transitory computer readable storage medium storing first computer instructions that cause the computer to perform the method provided by the corresponding method embodiments described above.
Referring to fig. 13, the electronic device includes: a second processor (processor)1301, a second memory (memory)1302, and a second bus 1303;
wherein,
the second processor 1301 and the second memory 1302 complete communication with each other through the second bus 1303;
the second processor 1301 is configured to call a second program instruction in the second memory 1302 to execute the method provided by the corresponding method embodiments.
The present embodiments provide a non-transitory computer readable storage medium storing second computer instructions that cause the computer to perform the method provided by the corresponding method embodiments described above.
Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
It should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A method for hybrid modulating multiple carriers, comprising:
acquiring a serial bit stream, and performing first preprocessing on the serial bit stream to obtain a plurality of groups of target bit streams;
respectively inputting each target bit stream into a corresponding Orthogonal Frequency Division Multiplexing (OFDM) modulation unit to obtain a plurality of corresponding subcarriers;
combining a plurality of sub-carriers to obtain a multi-carrier, and sending the multi-carrier to a receiving end;
wherein, a plurality of OFDM modulation units are connected in parallel to form a hybrid modulator of OFDM and FDM;
the method for obtaining a plurality of corresponding subcarriers by inputting each target bit stream into a corresponding Orthogonal Frequency Division Multiplexing (OFDM) modulation unit respectively comprises the following steps:
respectively inputting each target bit stream into a corresponding orthogonal frequency division multiplexing OFDM modulation unit, and sequentially carrying out constellation mapping, pilot frequency insertion, serial-parallel conversion, subcarrier mapping, N-point inverse discrete Fourier transform, parallel-serial conversion, cyclic prefix insertion, low-pass filtering, digital-to-analog conversion and up-conversion processing to obtain a plurality of corresponding subcarriers;
after combining the plurality of subcarriers, obtaining a multicarrier, and sending the multicarrier to a receiving end, specifically comprising:
combining a plurality of sub-carriers to obtain a multi-carrier, performing radio frequency amplification processing on the multi-carrier, and sending the multi-carrier subjected to the radio frequency amplification processing to a receiving end;
the OFDM modulation unit is used for modulating the 1 mapping symbol into 1 OFDM symbol of a time domain in a frequency domain, and simultaneously transmitting the 1 OFDM symbol in parallel by using N subcarriers; the OFDM and FDM hybrid modulator is used for modulating M analog signals containing 1 OFDM symbol by utilizing M up-conversion, and simultaneously transmitting the M analog signals of the OFDM symbol in parallel by utilizing the M up-conversion, so as to realize multi-carrier transmission of the M analog signals of the OFDM symbol by simultaneously transmitting N multiplied by M subcarriers in parallel in a time domain, wherein N is the number of the subcarriers, and M is the number of target bit streams.
2. A method for hybrid demodulation of multiple carriers, comprising:
receiving multiple carriers, and grouping the multiple carriers to obtain a plurality of sub-carriers;
respectively inputting a plurality of subcarriers into corresponding OFDM demodulation units to obtain a plurality of corresponding target bit streams;
performing second preprocessing on the plurality of target bit streams to obtain serial bit streams;
the OFDM demodulation units are connected in parallel to form a hybrid demodulator of OFDM and FDM;
the respectively inputting the plurality of subcarriers into the corresponding OFDM demodulation units to obtain a plurality of corresponding target bit streams specifically includes:
respectively inputting a plurality of sub-carriers into corresponding OFDM demodulation units, and sequentially carrying out up-conversion, analog-to-digital conversion, low-pass filtering, cyclic prefix removal, serial-to-parallel conversion, N-point inverse discrete Fourier transform, sub-carrier inverse mapping, parallel-to-serial conversion, channel compensation and constellation inverse mapping to obtain a plurality of corresponding target bit streams;
the OFDM demodulation unit is used for demodulating 1 OFDM symbol into 1 mapping symbol of a frequency domain in a time domain, and recovering N sub-OFDM symbols transmitted by N sub-carriers simultaneously into N mapping symbols of a corresponding frequency domain; the OFDM and FDM hybrid demodulator is configured to demodulate M analog signals containing M OFDM symbols using M downconversion frequencies, so that each OFDM demodulation unit obtains a corresponding analog signal containing 1 OFDM symbol, recovers 1 OFDM symbol through analog-to-digital conversion, and recovers N × M mapping symbols into an original serial bit stream, where N is the number of subcarriers and M is the number of target bit streams.
3. An apparatus for hybrid modulating multiple carriers, comprising:
the first bit stream processing module is used for acquiring a serial bit stream and performing first preprocessing on the serial bit stream to obtain a plurality of groups of target bit streams;
the subcarrier modulation module is used for respectively inputting each target bit stream into the corresponding orthogonal frequency division multiplexing OFDM modulation unit to obtain a plurality of corresponding subcarriers;
the multi-carrier acquisition module is used for combining a plurality of sub-carriers to obtain a multi-carrier and sending the multi-carrier to a receiving end;
wherein, a plurality of OFDM modulation units are connected in parallel to form a hybrid modulator of OFDM and FDM;
the subcarrier modulation module is specifically used for respectively inputting each target bit stream into a corresponding Orthogonal Frequency Division Multiplexing (OFDM) modulation unit, and obtaining a plurality of corresponding subcarriers after constellation mapping, pilot frequency insertion, serial-parallel conversion, subcarrier mapping, N-point inverse discrete Fourier transform, parallel-serial conversion, cyclic prefix insertion, low-pass filtering, digital-to-analog conversion and up-conversion processing are sequentially carried out;
the multi-carrier acquisition module is specifically used for combining a plurality of sub-carriers to obtain a multi-carrier, performing radio frequency amplification processing on the multi-carrier, and sending the multi-carrier after the radio frequency amplification processing to a receiving end;
the OFDM modulation unit is used for modulating the 1 mapping symbol into 1 OFDM symbol of a time domain in a frequency domain, and simultaneously transmitting the 1 OFDM symbol in parallel by using N subcarriers; the OFDM and FDM hybrid modulator is used for modulating M analog signals containing 1 OFDM symbol by utilizing M up-conversion, and simultaneously transmitting the M analog signals of the OFDM symbol in parallel by utilizing the M up-conversion, so as to realize multi-carrier transmission of the M analog signals of the OFDM symbol by simultaneously transmitting N multiplied by M subcarriers in parallel in a time domain, wherein N is the number of the subcarriers, and M is the number of target bit streams.
4. An electronic device, comprising:
at least one first processor; and
at least one first memory communicatively coupled to the first processor, wherein:
the first memory stores first program instructions executable by the first processor, the first processor invoking the first program instructions to perform the method of claim 1.
5. A non-transitory computer-readable storage medium storing a first computer program that causes a first computer to perform the method of claim 1.
6. An electronic device, comprising:
at least one second processor; and
at least one second memory communicatively coupled to the second processor, wherein:
the second memory stores second program instructions executable by the second processor, the second processor invoking the second program instructions to perform the method of claim 2.
7. A non-transitory computer-readable storage medium storing a second computer program that causes a computer to perform the method of claim 2.
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